3 * Copyright (C) 2011 Novell Inc.
5 * This program is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 as published by
7 * the Free Software Foundation.
11 #include <linux/slab.h>
12 #include <linux/xattr.h>
13 #include "overlayfs.h"
15 static int ovl_copy_up_last(struct dentry *dentry, struct iattr *attr,
19 struct dentry *parent;
21 struct path lowerpath;
23 parent = dget_parent(dentry);
24 err = ovl_copy_up(parent);
28 ovl_path_lower(dentry, &lowerpath);
29 err = vfs_getattr(&lowerpath, &stat);
36 err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat, attr);
43 int ovl_setattr(struct dentry *dentry, struct iattr *attr)
46 struct dentry *upperdentry;
48 err = ovl_want_write(dentry);
52 upperdentry = ovl_dentry_upper(dentry);
54 mutex_lock(&upperdentry->d_inode->i_mutex);
55 err = notify_change(upperdentry, attr, NULL);
56 mutex_unlock(&upperdentry->d_inode->i_mutex);
58 err = ovl_copy_up_last(dentry, attr, false);
60 ovl_drop_write(dentry);
65 static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry,
70 ovl_path_real(dentry, &realpath);
71 return vfs_getattr(&realpath, stat);
74 int ovl_permission(struct inode *inode, int mask)
77 struct dentry *alias = NULL;
78 struct inode *realinode;
79 struct dentry *realdentry;
83 if (S_ISDIR(inode->i_mode)) {
84 oe = inode->i_private;
85 } else if (mask & MAY_NOT_BLOCK) {
89 * For non-directories find an alias and get the info
92 alias = d_find_any_alias(inode);
99 realdentry = ovl_entry_real(oe, &is_upper);
101 /* Careful in RCU walk mode */
102 realinode = ACCESS_ONCE(realdentry->d_inode);
104 WARN_ON(!(mask & MAY_NOT_BLOCK));
109 if (mask & MAY_WRITE) {
110 umode_t mode = realinode->i_mode;
113 * Writes will always be redirected to upper layer, so
114 * ignore lower layer being read-only.
116 * If the overlay itself is read-only then proceed
117 * with the permission check, don't return EROFS.
118 * This will only happen if this is the lower layer of
121 * If upper fs becomes read-only after the overlay was
122 * constructed return EROFS to prevent modification of
126 if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) &&
127 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
131 err = __inode_permission(realinode, mask);
138 struct ovl_link_data {
139 struct dentry *realdentry;
143 static void *ovl_follow_link(struct dentry *dentry, struct nameidata *nd)
146 struct dentry *realdentry;
147 struct inode *realinode;
149 realdentry = ovl_dentry_real(dentry);
150 realinode = realdentry->d_inode;
152 if (WARN_ON(!realinode->i_op->follow_link))
153 return ERR_PTR(-EPERM);
155 ret = realinode->i_op->follow_link(realdentry, nd);
159 if (realinode->i_op->put_link) {
160 struct ovl_link_data *data;
162 data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL);
164 realinode->i_op->put_link(realdentry, nd, ret);
165 return ERR_PTR(-ENOMEM);
167 data->realdentry = realdentry;
176 static void ovl_put_link(struct dentry *dentry, struct nameidata *nd, void *c)
178 struct inode *realinode;
179 struct ovl_link_data *data = c;
184 realinode = data->realdentry->d_inode;
185 realinode->i_op->put_link(data->realdentry, nd, data->cookie);
189 static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz)
191 struct path realpath;
192 struct inode *realinode;
194 ovl_path_real(dentry, &realpath);
195 realinode = realpath.dentry->d_inode;
197 if (!realinode->i_op->readlink)
200 touch_atime(&realpath);
202 return realinode->i_op->readlink(realpath.dentry, buf, bufsiz);
206 static bool ovl_is_private_xattr(const char *name)
208 return strncmp(name, "trusted.overlay.", 14) == 0;
211 int ovl_setxattr(struct dentry *dentry, const char *name,
212 const void *value, size_t size, int flags)
215 struct dentry *upperdentry;
217 err = ovl_want_write(dentry);
222 if (ovl_is_private_xattr(name))
225 err = ovl_copy_up(dentry);
229 upperdentry = ovl_dentry_upper(dentry);
230 err = vfs_setxattr(upperdentry, name, value, size, flags);
233 ovl_drop_write(dentry);
238 ssize_t ovl_getxattr(struct dentry *dentry, const char *name,
239 void *value, size_t size)
241 if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE &&
242 ovl_is_private_xattr(name))
245 return vfs_getxattr(ovl_dentry_real(dentry), name, value, size);
248 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
253 res = vfs_listxattr(ovl_dentry_real(dentry), list, size);
254 if (res <= 0 || size == 0)
257 if (ovl_path_type(dentry->d_parent) != OVL_PATH_MERGE)
260 /* filter out private xattrs */
261 for (off = 0; off < res;) {
262 char *s = list + off;
263 size_t slen = strlen(s) + 1;
265 BUG_ON(off + slen > res);
267 if (ovl_is_private_xattr(s)) {
269 memmove(s, s + slen, res - off);
278 int ovl_removexattr(struct dentry *dentry, const char *name)
281 struct path realpath;
282 enum ovl_path_type type;
284 err = ovl_want_write(dentry);
288 if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE &&
289 ovl_is_private_xattr(name))
292 type = ovl_path_real(dentry, &realpath);
293 if (type == OVL_PATH_LOWER) {
294 err = vfs_getxattr(realpath.dentry, name, NULL, 0);
298 err = ovl_copy_up(dentry);
302 ovl_path_upper(dentry, &realpath);
305 err = vfs_removexattr(realpath.dentry, name);
307 ovl_drop_write(dentry);
312 static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
313 struct dentry *realdentry)
315 if (type != OVL_PATH_LOWER)
318 if (special_file(realdentry->d_inode->i_mode))
321 if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC))
327 static int ovl_dentry_open(struct dentry *dentry, struct file *file,
328 const struct cred *cred)
331 struct path realpath;
332 enum ovl_path_type type;
333 bool want_write = false;
335 type = ovl_path_real(dentry, &realpath);
336 if (ovl_open_need_copy_up(file->f_flags, type, realpath.dentry)) {
338 err = ovl_want_write(dentry);
342 if (file->f_flags & O_TRUNC)
343 err = ovl_copy_up_last(dentry, NULL, true);
345 err = ovl_copy_up(dentry);
349 ovl_path_upper(dentry, &realpath);
352 err = vfs_open(&realpath, file, cred);
355 ovl_drop_write(dentry);
360 static const struct inode_operations ovl_file_inode_operations = {
361 .setattr = ovl_setattr,
362 .permission = ovl_permission,
363 .getattr = ovl_getattr,
364 .setxattr = ovl_setxattr,
365 .getxattr = ovl_getxattr,
366 .listxattr = ovl_listxattr,
367 .removexattr = ovl_removexattr,
368 .dentry_open = ovl_dentry_open,
371 static const struct inode_operations ovl_symlink_inode_operations = {
372 .setattr = ovl_setattr,
373 .follow_link = ovl_follow_link,
374 .put_link = ovl_put_link,
375 .readlink = ovl_readlink,
376 .getattr = ovl_getattr,
377 .setxattr = ovl_setxattr,
378 .getxattr = ovl_getxattr,
379 .listxattr = ovl_listxattr,
380 .removexattr = ovl_removexattr,
383 struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
384 struct ovl_entry *oe)
388 inode = new_inode(sb);
394 inode->i_ino = get_next_ino();
395 inode->i_mode = mode;
396 inode->i_flags |= S_NOATIME | S_NOCMTIME;
400 inode->i_private = oe;
401 inode->i_op = &ovl_dir_inode_operations;
402 inode->i_fop = &ovl_dir_operations;
406 inode->i_op = &ovl_symlink_inode_operations;
414 inode->i_op = &ovl_file_inode_operations;
418 WARN(1, "illegal file type: %i\n", mode);